<br> Yellowtail flounder (Limanda ferruginea) On Georges Bank: Testing Models of Habitat Use <br>A better understanding of habitat requirements is mandated by federal fisheries law. One way to approach this issue is to examine factors that influence distribution. We are investigating how distribution changes with abundance, which is of particular interest in exploited populations that undergo large changes in abundance. Three theories have been proposed for the relationship between marine fish abundance and distribution: the Constant Density Model (CDM), the Proportional Density Model (PDM), and MacCall’s Basin Model (MBM) which incorporates the Ideal Free Distribution model of Fretwell and Lucas. The CDM predicts that the population’s range expands and contracts with changes in global abundance while local density does not vary. Habitat quality varies and the best habitats, conferring the highest fitness, remain occupied at lowest abundance. The PDM predicts that range remains constant and that local density varies with changes in abundance. Local density is highest in habitats that confer the highest fitness. The MBM predicts that there is density-dependent habitat use, such that both local density and species range vary with changes in abundance. Fitness should be the same across habitats because of these density-dependent processes. We are testing these theories using geospatial modeling and National Marine Fisheries Service trawl survey data. We test for changes in range by mapping non-zero catches at high and low population levels. We test for fitness changes across habitats by assessing spatial autocorrelation in fitness metrics (weight-at-length, weight-at-age). Results from analysis of yellowtail flounder (Limanda ferruginea) show evidence of spatial autocorrelation for both males and females except during spring spawning season when populations are low. Data from both the spring and fall survey shows that the area occupied by the species increases with increasing population size. While there are other predictions made by these models which we have not yet tested, these results support the constant density model.

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<span id="NAME">''' Karolina Fucikova'''</span>

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<br>''Bracteacoccus'' and its relatives: a case of cryptic genera <br>

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''Bracteacoccus'', one of the most common soil algae, is taxonomically interwoven with several other genera. In particular, its relationship with the morphologically similar ''Dictyococcus, Muriella'' and ''Pseudomuriella'' is quite tangled because these share a similar overall morphology with ''Bracteacoccus''. This has raised questions about the validity of these genera and the proper taxonomic disposition for their species. Phylogenetic relationships for a number of these taxa can be addressed using molecular sequence data obtained from live type strains. Using analyses of the 18S and rbcL genes, we determined that monophyly of ''Bracteacoccus'' can be achieved only by excluding four unrelated lineages that historically have been included under this name. Firstly, B. engadinensis belongs in the genus ''Pseudomuriella'', along with ''Dictyococcus schumacherensis''. Secondly, ''B. cinnabarinus'' and ''B. minutus'' group with ''Muriella zofingiensis'', a species with its own obscure taxonomic history. These three species are distinct from the true ''Muriella'' lineage (Trebouxiophyceae) and we propose to assign them to the resurrected genus ''Chromochloris'' (Chlorophyceae). Lastly, ''Dictyococcus'' was shown to be an unrelated lineage that can be reliably distinguished from ''Bracteacoccus'' based on chloroplast morphology. Our results indicate that ''Pseudomuriella, Chromochloris'' and ''Bracteacoccus'' are morphologically cryptic genera, representing closely related yet divergent lineages.

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[[Category:Graduate Research Symposium]]

[[Category:Graduate Research Symposium]]

[[Category:Graduate Student Resources]]

[[Category:Graduate Student Resources]]

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Latest revision as of 15:54, 18 March 2011

Saturday, March 19, 2011

Biology/Physics Building Room 130, 9:00am to ~ 4:00pm

The EEB Graduate Student Symposium is an all day event where graduate students present their research to other graduate students and faculty. Any EEB graduate student can present: BSMS, masters, PhD, old and new students. New graduate students usually present research ideas or preliminary data, while those more ‘seasoned’ students present their most recent results, often in preparation for upcoming spring and summer meetings.

Abstracts

Name Title
Abstract

Jose J. Pereira Yellowtail flounder (Limanda ferruginea) On Georges Bank: Testing Models of Habitat Use A better understanding of habitat requirements is mandated by federal fisheries law. One way to approach this issue is to examine factors that influence distribution. We are investigating how distribution changes with abundance, which is of particular interest in exploited populations that undergo large changes in abundance. Three theories have been proposed for the relationship between marine fish abundance and distribution: the Constant Density Model (CDM), the Proportional Density Model (PDM), and MacCall’s Basin Model (MBM) which incorporates the Ideal Free Distribution model of Fretwell and Lucas. The CDM predicts that the population’s range expands and contracts with changes in global abundance while local density does not vary. Habitat quality varies and the best habitats, conferring the highest fitness, remain occupied at lowest abundance. The PDM predicts that range remains constant and that local density varies with changes in abundance. Local density is highest in habitats that confer the highest fitness. The MBM predicts that there is density-dependent habitat use, such that both local density and species range vary with changes in abundance. Fitness should be the same across habitats because of these density-dependent processes. We are testing these theories using geospatial modeling and National Marine Fisheries Service trawl survey data. We test for changes in range by mapping non-zero catches at high and low population levels. We test for fitness changes across habitats by assessing spatial autocorrelation in fitness metrics (weight-at-length, weight-at-age). Results from analysis of yellowtail flounder (Limanda ferruginea) show evidence of spatial autocorrelation for both males and females except during spring spawning season when populations are low. Data from both the spring and fall survey shows that the area occupied by the species increases with increasing population size. While there are other predictions made by these models which we have not yet tested, these results support the constant density model.

Karolina FucikovaBracteacoccus and its relatives: a case of cryptic genera Bracteacoccus, one of the most common soil algae, is taxonomically interwoven with several other genera. In particular, its relationship with the morphologically similar Dictyococcus, Muriella and Pseudomuriella is quite tangled because these share a similar overall morphology with Bracteacoccus. This has raised questions about the validity of these genera and the proper taxonomic disposition for their species. Phylogenetic relationships for a number of these taxa can be addressed using molecular sequence data obtained from live type strains. Using analyses of the 18S and rbcL genes, we determined that monophyly of Bracteacoccus can be achieved only by excluding four unrelated lineages that historically have been included under this name. Firstly, B. engadinensis belongs in the genus Pseudomuriella, along with Dictyococcus schumacherensis. Secondly, B. cinnabarinus and B. minutus group with Muriella zofingiensis, a species with its own obscure taxonomic history. These three species are distinct from the true Muriella lineage (Trebouxiophyceae) and we propose to assign them to the resurrected genus Chromochloris (Chlorophyceae). Lastly, Dictyococcus was shown to be an unrelated lineage that can be reliably distinguished from Bracteacoccus based on chloroplast morphology. Our results indicate that Pseudomuriella, Chromochloris and Bracteacoccus are morphologically cryptic genera, representing closely related yet divergent lineages.